(1) Field of Invention
The present invention relates to a system for constructing a proactively secure secret sharing (PSS) protocol from a non-proactively secure secret sharing protocol and, more particularly, to a system for constructing a PSS protocol from a generic non-proactively secure secret sharing protocol.
(2) Description of Related Art
A proactively secure secret sharing (PSS) protocol is one that is secure under the proactive security model. PSS protocols allow data to be securely distributed among a group of servers (also referred to as players or parties in the cryptographic literature) in such a way that confidentiality and integrity are guaranteed as long as an adversary compromises no more than a fixed fraction of the servers in a certain period of time, called the refresh period. This remains true even if the adversary is allowed to eventually compromise all the servers; the main requirement is that no more than a fixed fraction is compromised during any given stage (i.e., time between two subsequent refreshes) of the operation of the PSS protocol.
The construction of a PSS protocol using a SHARE protocol would be advantageous. Literature Reference No. 4 (see the List of Incorporated Literature References) describes proactive SHARE refreshing, but does not have a construction from generic SHARE protocols. In particular, Literature Reference No. 4 is only cryptographically secure in the asynchronous model. Information theoretically secure protocols are more desirable, because they do not rely on the hardness of computational assumptions so there is no threat of such assumptions being rendered insecure due to advances or breakthroughs in the state of knowledge in computer science and other related fields. Heuristically, information theoretically secure protocols are also more efficient than cryptographically secure protocols.
Thus, a continuing need exists for construction of a PSS protocol from any generic non-proactively secret sharing protocol that can be information theoretically secure.